1. Field of the Invention
This invention relates to an imaging system which is capable of seeing or photographing objects over a long range without changing a focus, i.e., without changing the position of the focal plane and with a high resolution and, even when obtained images are blurred and the resolution is degraded by atmospheric turbulence, suppressing this degradation.
2. Description of the Prior Art
In the conventional imaging systems, the optical lenses or reflection mirrors which are the components of the device have been adopted on the condition that they are free from spherical aberration, and optical devices, such as the correcting plates, are used for the purpose of correcting the spherical aberration.
Conventional cameras are required to stop down the lens aperture for the purpose of increasing the focal depth and hence the depth of field. The stopping down of the lens aperture results in reduction of the light intensity of reception and degrading the resolution.
Furthermore, a conventional imaging system in the environment condition with atmospheric turbulence suffers image blurring and therefore, encounter difficulty in taking images of high resolution. For the purpose of obtaining an image of high resolution from such a fluctuating image, image processing techniques including the speckle interferometry have been proposed and used. In the conventional image processing techniques, however, special equipment and a long computation time is necessary. Adaptive optics is a new technique to compensate image blurring actively in real time. But, this technique needs large scale and complicated equipment.
In the conventional technique using the optical lenses free from spherical aberration, a camera requires the lens aperture to be stopped down for the purpose of increasing the focal depth. This stopping down of the lens aperture results in reducing the light intensity of reception and degrading the resolution. In the environment condition of atmospheric turbulence, it is necessary to use a compensating optical device, such as adaptive optics, or use a computerized image-processing technique.
This invention has been proposed in view of the state of affairs mentioned above and is aimed at providing an imaging system which is capable of obtaining images with a large focal depth and as well suppressing the image blurring caused by atmospheric turbulence.
This invention is directed toward overcoming problems inherent in conventional techniques by adapting a special optical system, namely by using a telescope or a wavefront controlling plate which is set in front of a fundamental image formation component, such as a camera. By this system, the phase of light is delayed in accordance with increase of radial distance from the optical axis. That is, by controlling the wavefront of light during the course of image formation as specifically described herein below, this invention is enabled to deepen the focal point of a formed image. It is further enabled to suppress image blurring caused by atmospheric turbulence, and form an image of objects with a high resolution over a long distance.